|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1995 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1994 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Formation of learning involves increase in production of protein, mRNAs and so forth in response to stimuli. Yamamoto et al. (1993) reported about FOS-protein in the parabrachial nucleus (PBN) of rats in reponse to various taste solution in normal rats, and to conditoned taste after the animal learned conditioned taste-aversion (CTA). In the present project, we studied the production of FOS protein in insular cortex including the gustatory cortical area in mice at CTA formation, in reference to that in the PBN.
When mice drunk basic taste solution, different taste induced FOS protein in different subnucleus of the PBN : NaCl, sucrose snd HCl induced many FOS-positive neurons at the lateral central subnucleus, and HCl produced them at the ventral subnucleus, as well. Quinine yielded a few FOS-postive neurons at the lateral external subnucleus. No FOS-positive neuron was found at the region where taste relay neurons have been located previously. In rats, FOS-positive neurons were induced
in some other subnucleus, as well. In the insular cortex, sucrose induced many FOS-positive neurons at primary somatosensory area and granular insular cortex, while other taste stimuli including NaCl a fewer number of such neurons in the dysgranular insular cortex. After mice received salty taste and visceral illness by drinking LiCl, FOS-posiitive cells were seen at the lateral central and lateral external subnucleus of the PBN.Intraperitoneral injection of LiCl which induces only visceral illness produced FOS-positive neurons only at the lateral external subnucleus. In both cases, FOS-positive cells were noted at the dysgranular insular cortex. After mice learned CTA to NaCl or sucrose by associating it with visceral illness, either conditioned stimulus induced FOS-positive cells at the lateral central and ventral subnucleus of the PBN,and at the dysgranular cortex, though such a stimulus induced them only at the lateral external nucleus of the PBN.These findings were confirmed by observing induction of c-fos mRNA by in situ hybridization.
The present results indicate that neural circuits involved in CTA differ in some degree between mice and rats. Less